The present invention relates to a new and improved construction of a shaft coupling and a method of operating the same in order to positively interconnect with an interference fit or frictionally two shafts which are to be operatively coupled with one another, in order to reliably transmit a rotational moment or torque between such two shafts.
In its more specific aspects, the shaft coupling of the present development serves for the frictional connection of two coaxially arranged shafts each having substantially cylindrical shaft ends or end sections. The shaft coupling contains an inner sleeve or bushing possessing a substantially cylindrical bore having a slight over-dimension in relation to the cylindrical end sections or portions of the shafts and a slightly conical outer surface or taper. Additionally, there is provided an outer sleeve or bushing possessing an inner conical surface or taper which is suitable for coacting with the conical outer surface or taper of the inner sleeve. The outer sleeve is provided with a bore for the infeed of hydraulic medium at a high pressure between the conical surfaces or tapers of the inner and outer sleeves. The outer sleeve can be displaced by using a relatively modest amount of force upon the inner sleeve into an operating or working position in which the inner sleeve is compressed by the outer sleeve and firmly pressed against the end portions or sections of the shafts in such a manner that there is provided a frictional connection between both of the shafts. The outer sleeve has support sections or portions which, in the operating position of the shaft coupling, are intended to encircle the end portions of the shafts. Between such support portions or sections there is located an intermediate portion or section which, in the operating position of the shaft coupling, is located at the region between both of the shafts.
Such types of shaft couplings, among other things, are used for interconnecting propeller shafts of marine vessels with their drive shafts. They have the advantage that there can be avoided the use of keyways, they require very little space and can be easily mounted and again dismantled.
However, the heretofore known constructions of such shaft couplings are associated with the drawback that during the driving-up of the outer sleeve upon the inner sleeve the latter must be supported along its entire length. At the location wherever there is present a gap, typically between the confronting end portions or sections of the shafts to be interconnected, in other words at those locations where the inner sleeve is not supported, the inner sleeve can become damaged by virtue of the high prevailing hydraulic pressures.
Thus, for instance, to counteract or mitigate against this appreciable shortcoming both ends of the shafts which are to be interconnected must be arranged or adapted so as to abut one another without the formation of any intermediate gap therebetween. Under certain circumstances this can require that there be undertaken expensive adaptation or modification work during the mounting of the shaft coupling upon the shafts.
On the other hand, situations are encountered in practice, such as for example in the case of adjustable pitch propellers, where two hollow shafts should be interconnected which contain in their hollow spaces or passageways tubular pipes or conduits. As a general rule, these tubular pipes are provided with pipe couplings at the connection location of both shafts, in order to thus be able to disconnect, by means of such pipe couplings, the propeller along with its propeller shaft completely from the drive shaft.
With the present day constructions of shaft couplings of the aforementioned type it is necessary, in the aforementioned instance, to fit bipartite ring-shaped insertion elements into the intermediate space or gap between both of the shaft ends, in order to provide an effective support of the inner sleeve during the assembly of the shaft coupling which entails drawing or driving-up the outer sleeve along the inner sleeve. Inasmuch as this work only can be performed after the installation of the propeller at the marine vessel it is both cumbersome and expensive.